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Yamaha 2-stroke, 200 hp V-6 from 1987 correct compression

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nicolay94

New member
Hi,

I have a yamaha 2-stroke V-6 from 1987, 200hp, what compression should i reach with this engine? Found nothing in the yamaha service manual.

Cheers
 
minimum compression pressure refer below.

(reference data) compression pressure 101.5 PSI
(minimum) compression pressure 75.4 PSI

it's model Yamaha 200AET (2,596 cc) v6.

have a nice day.
 
Jinsoo said:
minimum compression pressure refer below.

(reference data) compression pressure 101.5 PSI
(minimum) compression pressure 75.4 PSI

it's model Yamaha 200AET (2,596 cc) v6.

have a nice day.
Click to expand...


Thanks. Are you sure that the compression can be as low as 75,4 PSI? May I ask where you get this information from?
 
They don't really post the comp. figures because the results can vary so much with the
equipment and the procedures.

The important thing is the results are all within 5% of each other.
My gauge on a 200 Yam gets 150# on a healthy motor.
A Harbor Freight gauge gets 110# some read worse??

Last week did a test on a 2 2005 200 hp
One motor had 150 all 6
The other had 130 155 140 150 150 150

Get a good gauge and look on U tube for directions.

What results did you get?
If all 6 are the same???
 
Jerryjerry05 said:
They don't really post the comp. figures because the results can vary so much with the
equipment and the procedures.

The important thing is the results are all within 5% of each other.
My gauge on a 200 Yam gets 150# on a healthy motor.
A Harbor Freight gauge gets 110# some read worse??

Last week did a test on a 2 2005 200 hp
One motor had 150 all 6
The other had 130 155 140 150 150 150

Get a good gauge and look on U tube for directions.

What results did you get?
If all 6 are the same???
Click to expand...


Hi Jerry,

I did the test at cold engine and without any throttle and got 94 94 87 94 87 87
With a lean engine and full throttle I got 101,5 101,5 95 101,5 95 95

Remember this Is a 2 stroke engine and a V6. So dont think I will ever end up at the 150 range anyway.
 
The Yams I tested are 2 stroke v-6's.

What gauge you using? a screw in or the one you shove in the hole?
Harbor freight tools are junk.

Your results: 1st test. 3 at 94 3 at 87 that's 6-7% difference.
That's acceptable.

Do you use Yamaha's ring free?
Or use a decarb?
Yam oil is supposed to run best and not carbon up.

I bought a snake camera for my Android phone. $11
Works pretty good for checking the cylinder walls.
Best to do it under a cover or after dark.
 
Jerryjerry05 said:
The Yams I tested are 2 stroke v-6's.

What gauge you using? a screw in or the one you shove in the hole?
Harbor freight tools are junk.

Your results: 1st test. 3 at 94 3 at 87 that's 6-7% difference.
That's acceptable.

Do you use Yamaha's ring free?
Or use a decarb?
Yam oil is supposed to run best and not carbon up.

I bought a snake camera for my Android phone. $11
Works pretty good for checking the cylinder walls.
Best to do it under a cover or after dark.
Click to expand...


Thats strange. Your motors are age 2005? mine is 1987, might have to do With that fact… In the service manual Yamaha informs that the compression ratio is from 5,8 to 6,8 on the 1987 modell. Not sure if its correct to convert this by multypling the atmosferical pressure at sea Level(14,696) but if so, you get about my number regarding the PSI.


Thanks for the tip on a snake cam, I have one in order and will check the cylinder when it gets here. I still think that Yamaha made the early V6 engines as low compression engines. But they might have change that in the 2000`s, regarding Your PSI to be so high.
 
That's very possible, the early OMC had motors with lower comp #s too.

I've found if you run in salt water (even a little) you should change the head gaskets every couple of years.
The salt residue builds up around the hottest spots and can lead to gasket failure.
 
Jerryjerry05 said:
That's very possible, the early OMC had motors with lower comp #s too.

I've found if you run in salt water (even a little) you should change the head gaskets every couple of years.
The salt residue builds up around the hottest spots and can lead to gasket failure.
Click to expand...


My engine was rebuild in 2008, and has only been used in on a lake since. Not many hours at all since the rebuild.
 
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